A solid oxide fuel cell (referred to as SOFC below) as a fuel cell has been known as a general-purpose and high-efficiency fuel cell. Since an operating temperature of the SOFC is set to be high to increase an ion conductivity, compressed air discharged from a compressor of the gas turbine can be used as air (oxidant) supplied to a side of an air electrode. Also, high-temperature exhausted fuel gas exhausted from the SOFC can be used as a fuel of the combustor of the gas turbine.
Therefore, for example, as described in Patent Literature 1, various power generation systems in which the SOFC, SOFC, the gas turbine, and the steam turbine are combined have been proposed as a power generation system which can achieve a high-efficiency power generation. In a combined system described in Patent Literature 1, the gas turbine includes a compressor for compressing air and supplying it to the SOFC and a combustor for generating combustion gas from the exhausted fuel gas exhausted from the SOFC and the air.
For example, Patent Literature 2 discloses a fuel cell system including a combustor for burning exhausted fuel gas to be exhausted from a fuel cell. The combustor includes a primary combustion chamber and a secondary combustion chamber. The exhausted fuel gas from the fuel cell is jetted from a burner, and the primary combustion chamber performs primary combustion of the exhausted fuel gas by using primary air. The secondary combustion chamber is connected to the primary combustion chamber via a communication passage having a gas passage narrower than the primary combustion chamber and performs secondary combustion of the gas from the primary combustion chamber by using secondary air. The burner includes triple blowoff port. In the triple blowoff ports, a torch flame blowoff port for jetting an ignition torch flame is arranged at the center, and an annular exhausted fuel blowoff port for jetting the exhausted fuel gas is arranged outside the torch flame blowoff port. Also, a circular exhausted air blowoff port for jetting exhausted air to outside the exhausted fuel blowoff port is concentrically arranged. The burner also includes a plurality of auxiliary fuel blowoff ports, which passes through the exhausted air blowoff port and jets the auxiliary fuel, in the exhausted air blowoff port.
Also, for example, Patent Literature 3 discloses a fuel supply method for the combustor for supplying at least two kinds of fuels having different calories from each other to the combustor. At the time of starting operation of the gas turbine, a high calorie fuel and low calorie fuel are supplied to the combustor by using both a first fuel supply system for supplying the high calorie fuel to a first nozzle included in the combustor and a second fuel supply system for supplying the low calorie fuel to a second nozzle included in the combustor. When an output of the gas turbine reaches the output which can realize continuous operation with the low calorie fuel, the supply of the high calorie fuel to the combustor is interrupted, and the low calorie fuel is supplied to the combustor.